A motorcycle in which a front wheel is attached by a swing arm to a body frame is disclosed in JP 2002-500133 A. Main portions of the motorcycle will be described below with reference to FIGS. 19 and 20 hereof.
As shown in FIG. 19, in the motorcycle 200, a lower swing arm 203 and a middle swing arm 204 extend frontward from a body frame 201 or an engine 202. A distal end of the lower swing arm 203 and a distal end of the middle swing arm 204 are connected by V-shaped plates 205.
A steering handle 208 is fitted in a head pipe 207 that is provided at a front part of the body frame 201. A handle link 209 that is capable of vertically bending is connected to a lower end of the steering handle 208. A knuckle arm 210 is connected to a lower end of the handle link 209. The knuckle arm 210 is a member for directly steering (pivoting) a front wheel 211.
An upper swing arm 212 extends frontward from the body frame 201, and an upper part of the knuckle arm 210 is connected to a distal end of the upper swing arm 212.
As shown in FIG. 20, the front wheel 211 comprises a tire 214; a rim 215 for directly supporting the tire 214; spokes 216 extending from the rim 215; and a hub 217 connected to the spokes 216.
A hub body 219 is accommodated within the hub 217 via an axle bearing 218 so as to be capable of relative rotation. A pivot pin 221 extending from an axle 220 is fitted into the hub body 219. A lower end of the knuckle arm 210 is connected to the hub body 219.
A spline 222 is formed in an end part of the axle 220. A coupling 223 is fitted onto the spline 222 and secured to the V-shaped plates 205. The distal end of the upper swing arm 212 is connected to the knuckle arm 210 via a ball bearing 224.
The pivot pin 221 is stationary in the Figure because the axle 220 is secured by the V-shaped plates 205, 205. The hub body 219 rotates about the pivot pin 221, whereby the front wheel 211 is steered. The front wheel 211 rotates about the pivot pin 221 and about the axle 220.
In FIG. 19, the length of the upper swing arm 212 changes when the lower swing arm 203 and the middle swing arm 204 swing together in the vertical direction. Specifically, the distance between a pin 225 provided on the body frame 201 and the ball bearing 224 provided in the knuckle arm 210 changes. The upper swing arm 212 is connected to the pin 225 via an intermediate pin 226 and an auxiliary link 227 in order for such changes in distance to be addressed.
As is evident from the description above, the motorcycle 200 must be provided with the lower swing arm 203, the middle swing arm 204, the upper swing arm 212, the intermediate pin 226, and the auxiliary link 227. Problems therefore arise in that the structure of the motorcycle 200 is complex, and costs associated with the manufacture of the motorcycle 200 are high.
A demand has accordingly arisen for a motorcycle having a front wheel attached to a body frame using swing arms to have a simpler structure that allows manufacturing costs to be lowered.